Macrolide antibiotics accumulate preferentially within different cells of subjects, especially within phagocyte cells such as mononuclear peripheral blood cells, and peritoneal and alveolar macrophages. (Gladue, R. P. et al, Antimicrob. Agents Chemother. 1989, 33, 277-282; Olsen, K. M. et al, Antimicrob. Agents Chemother. 1996, 40, 2582-2585). Inflammatory effects of some macrolides have been described in the literature. For example, the anti-inflammatory effect of erythromycin derivatives (J. Antimicrob. Chemother. 1998, 41, 37-46; WO Patent Application No. 00/42055) and azithromycin derivatives has been described (EP Pat. Br. 0283055). Anti-inflammatory effects of some macrolides are also known from in vitro and in vivo studies in experimental animal models such as in zymosan-induced peritonitis in mice (J. Antimicrob. Chemother. 1992, 30, 339-348) and endotoxin-induced neutrophil accumulation in rat trachea (J. Immunol. 1997, 159, 3395-4005). The modulating effect of macrolides upon cytokines such as interleukin 8 (IL-8) (Am. J. Respir. Crit. Care. Med. 1997, 156, 266-271) and interleukin 5 (IL-5) (EP Pat. Br. 0775489 and EP Pat. Br. 771564) is known as well.
Macrolides have the property of accumulating within immune system cells recruited to the site of inflammation, especially phagocytic cells: Pascual A. et al. Clin. Microbiol. Infect. 2001, 7, 65-69. (Uptake and intracellular activity of ketolide HMR 3647 in human phagocytic and non-phagocytic cells); Hand W. L. et al. Int. J. Antimicrob. Agents, 2001, 18, 419-425. (Characteristics and mechanisms of azithromycin accumulation and efflux in human polymorphonuclear leukocytes); Amsden G. W. Int. J. Antimicrob. Agents, 2001, 18, 11-15. (Advanced-generation macrolides: tissue-directed antibiotics); Johnson J. D. et al. J. Lab. Clin. Med. 1980, 95, 429-439.(Antibiotic uptake by alveolar macrophages); Wildfeuer A. et al. Antimicrob. Agents Chemother. 1996, 40, 75-79. (Uptake of azithromycin by various cells and its intracellular activity under in vivo conditions); Scorneaux B. et al. Poult. Sci. 1998, 77, 1510-1521. (Intracellular accumulation, subcellular distribution, and efflux of tilmicosin in chicken phagocytes); Mtairag E. M. et al. J. Antimicrob. Chemother. 1994, 33, 523-536. (Investigation of dirithromycin and erythromycylamine uptake by human neutrophils in vitro); Anderson R. et al. J. Antimicrob. Chemother. 1988, 22, 923-933. (An in-vitro evaluation of the cellular uptake and intraphagocytic bioactivity of clarithromycin (A-56268, TE-031, a new macrolide antimicrobial agent); Tasaka Y. et al. Jpn. J. Antibiot. 1988, 41, 836-840. (Rokitamycin uptake by alveolar macrophages); Harf R. et al. J. Antimicrob. Chemother. 1988, 22, 135-140. (Spiramycin uptake by alveolar macrophages).
Macrolide antibiotics appear to have a promising role in the management of diseases of chronic airway inflammation, distinctly separate from their bactericidal activity. Over the last fifteen years, their success in human clinical trials, particular in diseases such as diffuse panbronchiolitis and cystic fibrosis, has prompted both in vitro and in vivo investigations to determine the mechanisms by which this family of antibiotics modulate the immune response. A large body of evidence suggests that macrolides directly target multiple components of the inflammatory cascade that occur independent of bactericidal/bacteriostatic effects. (W. C. Tsai, Current Pharmaceutical Design, 2004, 10, 3081-3093).
There is a great need to understand mechanisms that control inflammation within the lung. This imperative coincides with a revolution in cellular and molecular biology which should provide the tools necessary for lung biologists to clarifying the mechanism(s) by which macrolides exert immunomodulatory effects in the setting of pulmonary inflammation, and establishing potential therapeutic strategies based on the elucidated mechanism(s). For example, it was shown that azithromycin specifically binds to α1-acid glycoprotein from serum using dialysis in combination HPLC methods (Castearena et al., J Chemother. 1995, 7 Suppl 4:26-8).
Photoaffinity labeling is a technique in which a photochemically reactive molecular entity, specifically associated with a biomolecule, is photoexcited in order to covalently attach a label to the biomolecule, usually via intermediates (IUPAC Compendium of Chemical Terminology, 2nd Edition, 1997). Photoaffinity labeling is important methodology in biological science widely used for the analysis of structural aspects which are related to specific functions of the target biological macromolecular systems. The method requires photoreactive groups which generate highly reactive intermediates, usually nitrene and carbene as the key structure of photoaffinity probes (Hatanaka Y. et al., Heterocycles, 1993, 35, 997-1004).
The use of macrolide photoaffinity analogs allows the study of protein-macrolide interactions at the molecular level. Photoaffinity labeling technique can be used to determine which specific macrolide binding proteins are the targets of drugs.